1. Technical Field
The present invention relates to a piezoelectric vibrating element integrally including a main vibration section and an outer frame surrounding it in the same piezoelectric substrate, and a piezoelectric vibrator.
2. Related Art
Recently, as down-sizing of electronic apparatuses has been advanced, there have been demands for miniaturizing piezoelectric vibrators used for the electronic apparatuses and piezoelectric vibrating elements used for the piezoelectric vibrators and making them thinner. To meet such demands, a piezoelectric vibrating element 500 shown in FIGS. 10A and 10B, for example, has been proposed. FIGS. 10A and 10B illustrate an AT cut vibrating element using a quartz crystal substrate as an example of related art piezoelectric vibrating elements, where FIG. 10A is a plan view and FIG. 10B is a front sectional view. As shown in FIGS. 10A and 10B, the piezoelectric vibrating element 500 includes a main vibration section 502 formed in the center portion of a quartz crystal substrate (quartz crystal wafer) 501, an outer frame section 503, and junction sections 504. The main vibration section 502 has its outer shape formed by a through-hole 505 provided in the outer peripheral portion, and is integrally connected to the outer frame section 503 by two junction sections 504 having no through-hole 505. The junction section 504 has a width of about 200 μm and is formed so that both surfaces 508 and 509 are formed to be closer to the center in the thickness direction than both surfaces 506a and 506b of the main vibration section 502 or both surfaces 507a and 507b of the outer frame section 503. Accordingly, the both surfaces 508 and 509 of the junction section 504 are connected with the both surfaces 506a and 506b of the main vibration section 502 or the both surfaces 507a and 507b of the outer frame section 503 to form steps in connecting portions. The outer frame section 503 is formed in a shape substantially surrounding the outer shape of the main vibration section 502 (e.g., JP-A-7-212171, an example of related art). Although not shown in the drawing, a piezoelectric vibrating element including the main vibration section and the outer frame section connected with each other by using four junction sections is also disclosed (e.g., Japanese Patent No. 3,390,348, another example of related art).
As described above, however, the junction section 504 has a small thickness and a small width, and therefore the strength of the junction is not sufficient such that the junction section 504 is easy to break upon impact such as, for example, if the junction section 504 is dropped. Since the junction section 504 is formed to have steps in the connecting portions of both surfaces 508 and 509 with both surfaces 506a and 506b of the main vibration section 502 or both surfaces 507a and 507b of the outer frame section 503, stress concentration occurs at corner portions to facilitate breakage of the junction section 504 when an impact such as dropping or the like is imposed. The breakage of the junction section 504 causes the main vibration section 502 to be detached from the outer frame section 503, resulting in a problem that it becomes impossible for the piezoelectric vibrating element 500 to fulfill its function.